1. Field of the Invention
The present invention relates to an apparatus for producing fiber aggregate, and more particularly, it relates to an apparatus for continuously producing fiber aggregate in which most fibers are one-dimensionally oriented. "One-dimensional orientation" means that many fibers are oriented in about the same direction. This definition applies not only to the fiber aggregate but also to the orientation step to be mentioned later.
2. Discussion of the Background
Heretofore, fiber aggregate of short fibers or whiskers has been produced by using one of the conventional apparatuses mentioned below.
The first one is a centrifugal forming apparatus as shown in FIG. 4 (disclosed in Japanese Patent Laid-open No. 65200/1985). In operation of this apparatus, an aqueous suspension of silicon carbide whiskers or the like is fed through the supply pipe 24 to the porous cylindrical vessel 23 which is lined with the filter film 25 and disposed in the outer cylinder 21. The hollow fiber aggregate 26 is formed by centrifugal action. Water is discharged from the water outlet 22.
The second one is a suctional forming apparatus as shown in FIG. 5. In operation of this apparatus, a prescribed amount of fiber-containing fluid 34 is fed to the cylinder 31, and a pressure is applied to the fluid 34 by the pressing plunger 32 arranged above the cylinder 31. At the same time, the filtrate is removed by suction through the filter 33 disposed at the bottom of the cylinder 31. Thus the fibers in the fluid are oriented and aggregated.
The fiber aggregate formed by the above-said centrifugal forming apparatus or suctional forming apparatus is not composed of one-dimensionally oriented fibers, but is composed mainly of two- or three-dimensionally oriented fibers. The fiber aggregate with such orientation has a disadvantage that it does not provide a sufficient strength in the desired one-dimensional direction when incorporated into fiber-reinforced metal (referred to as FRM hereinafter). Additional disadvantages are the low volume ratio of fiber and the excessive spring back at the time of compression molding.
With the conventional apparatuses, it was impossible to produce one-dimensional oriented fiber aggregate and it was only possible to produce two- or three-dimensionally oriented fiber aggregate. It was also impossible to produce fiber aggregate continuously.
It is an object of the present invention to provide an apparatus for producing fiber aggregate in which most fibers are one-dimensionally oriented. The fiber aggregate produced by using the apparatus of this invention has a high fiber volume ratio and a low degree of spring back. When incorporated into FRM, it provides FRM having a high strength in the desired one dimension. With the apparatus of the present invention, it is possible to produce one-dimensionally oriented fiber aggregate continuously by using the sheet drive unit which moves the long filter sheet horizontally.